I. Mechanissms of consignment of cells to determinant-specific immunocompetency; II. Promoters and amplifiers of antibody biosynthesis in cell culture; III. Initiation and suppression of determinant specific antibody responses in cell culture. Experiments are designed to understand cellular pathways of antigen directed antibody biosynthesis. It is the aim of these studies to devise means of selective regulation of the synthesis of antibodies by imposing selective pressures upon cooperating and/or competing cell populations. Natural immunogenic macromolecules and particles are used as carriers of chemically substituted defined determinant groups. Such immunogens are used to stimulate rodent immunocytes in an in vivo and in vitro experimental model. Fundamental questions are asked relative to cell cooperative relationships between regulatory T-lymphocytes which augment or suppress the antibody secreting potential of B-lymphocytes. The role of macrophages in this relationship is being studied as well. Use of cells from animals which are genetically deficient of T-cells, but possess all other components (e.g., nude mice) facilitate our experimental results.